Hydraulic steering and control device



Mmh' 1940- c. u. BALLARD l 2,192,175

HYDRAULIC STEERING AND CONTROL DEVICE Filed Sept. 17, 1935 4 SheetS-Sheel 1 95W?" @www vMarch 5, 1940.v c. U.- BALLARDA 2,192,175

HYDRAULIC STEERING AND CONTROL DEVICE Filed Sept. 1'7, 1935 4 Sheets-Sheet 2 .7 3 ai I k7; 4 l 175 157 22s 16a 210 ff/178 165 152 E L5 16a l /zoo l 171 216 f/9z 215 239 E y/ g/ 21s l i /lm 219 5 g f 5 4 217 v 22o 1.88 218 233 I 2.94 l a 92 2- i 185 15o l gi? eao/ n 28.5 g

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HYDRAULIC STEERING AND CONTROL DEVICE Filed sept 17, 1955 4 sheets-sheet s' mili in March 5, 1940. c. U. BALLARD 2,192,175

HYDRAULIC STEERING AND CONTROL DEVICE Filed Sept. 17, 1935 4 Sheets-Sheet 4 Mana' wezfs d nzme jl/05; A j# Mw pressure.

Patented Mar. 5, 1940 PATENT OFFICE HYDRAULIC STEERING AND CONTROL DEVICE Charles'll. Ballard, Inglewood, Calif.

Application September-17, 1935, Serial No. 40,912

4 Claims.

tor, and the ailerons of an airplane may be suitably actuated hydraulically.

Another object and feature of my invention is using somewhat the sam'e type of mechanism in r both the compressor for generating the pressure ln the fluid and ln the actuator by which the uid under pressure is applied to a useful purpose in developing the angular motion. Thus, in my invention I may have in the lcompressor a double ended piston, which may be reciprocated, for instance, by gears or by a screw type of mechanism to create a positive pressure at one end of the cylinder and the same type of mechanism operating in the reverse manner may be used in the actuator. Thus, the'actuators being provided with double ended pistons when moved by the hydraulic fluid under pressure through gears or a screw connection may operate the device to be rotated in an arc.

Another object and feature of my invention is in constructing both the compressors and the actuators in such a manner that they are practically leakproof, having no operatingparts extending through a casing or the like subject to Hence, no stufling boxes or the equivalent are required in the mechanism which gives -motion to the double ended piston in the compressor nor stufng boxes or such equipment necessary in the actuator for turning the element which has an angular movement in reference to the movement in reciprocating the double ended piston.

A further general object and feature of my invention is in the compressors employing a cylinder in which operates a double ended piston, each end of the cylinder beingl connected to a hydraulic pipe line 'and providing in each pipe line a compensating relief valve, such valve being designed andconstructed to'permit the out- 0 let flow of fluid from the hydraulic system when the fluid in the hydraulic system expands through heat-,1 and therefore must have an outlet for the" excess fluid. This relief valve is also constructed and designed to. supply liuid to replace a deficiency in the systemland thus-has a double func- Thus, my inven" rotation of the screw, the splines operating ol.- en -54.5)

tion in relieving the lluid under excess pressure in the system and again replacing and supplying fluid to the system to assure there ls'a sucient quantity for operatingy mechanism under all circumstances. The relief valve may be set to release iiuid under a predeterminedl pressure but this release is at a very slow rate in order to take care of the expansion of the fluid but not to allow fluid to be forced outwardly through the relief valve due to the operation of the compressor. Thus, the operation of the compressor substantially closes the relief valve and connes the operating fluid to the hydraulic system but when the fluid expands through heat and in the intermittent periods between opera- '15 tion of the compressor this excess fluid may escape. f

A feature of my invention in one type of mechanism is the employmenfof a cylinder having a double ended-piston connected by a rack. This 20 rack is actuated by av system of gears, the initial movement being by a rotatable steering wheel.

From each' end of the cylinder hydraulic pipes lead to the actuator. Such actuator has a cylinder with a double ended piston, the. piston having a rack and in the movement of the piston the rack meshes with a segmental gear and thus causes the rotation either of the device connected to theu segmental gear Aor if this gear should be held stationary,- to the piston having the rackj and thus the cylinders in which the piston is mounted.

In another form of my invention the double ended piston is arranged to operate in a cylinder and .be reciprocated by a screw and nut of which either the screw or nut may be rotatable and, for instance, when using a screw this may be turned by a steering wheel, thus causing a longitudinal movement of the nut, the nut having' splines or the like to prevent its rotation relative to the cylinder, and such nut is provided with a sleeve connected by pins or the like to the piston, thus causing 3a reciprocation in opposite directions ofthe piston and developing hydraulic pressure at either end of the f-ylinderf'rom both ends of which 'the supply pipes lead to the actuator.

'I'he screw type of actuator may be of a reverse character and, for instance, the double ended piston may have a screw and splines to prevent through a relatively fixed structure, and the screw portion engaging a nut forming part of the cylinder. Therefore under the operation .of the fluid from the compressor as the piston is moved in one direction the nut and, hence, the cylinder,

will be caused to rotate and this rotation may be communicated to the part to be movedsuch as the steering axle of a vehicle wheel or the rudder post of a vessel or the like. In this type of device the action may be the reverse; the cylinder may be held stationary and have the splines operate the turning part of the mechanism.

may be readily moved.

the em Another object and feature of my invention is the development of a simplified double acting piston which may be connected directly to a drag link for operating a steering mechanism. In this case the piston operates in a cylinder, the cylinder being' provided with a slot von one side through which extends a swivel connectionjfor the drag link. Thus, this connection may be substantially at the center of the double ended piston.

Another feature of my invention involves a locking valve between the compressor and the actuators, such valve being connected across the two pressure pipes from the compressor cylinder to the actuator, such being a two-way valve, and such valvefwhen in thel closed position gives a connection from one end of the compressor to 'one end of the actuator and from the other end of the compressor to the other end of the actu-- ator. When the valve is turned to its open position it affords a free connection between both ends of the compressor and also between .both ends of the actuator cylinder. This allows the steering wheel to be rotated `in eitlier direction, giving a movement of the liquid between both ends of the compressor but on account 'of the friction resistance of the gears or of -a connection the actuator pistons cannot be readily operated to circulate the iuid between the two ends of the actuator cylinder and thus for practical However, where the friction in the actuator is comparatively. low and the valve is in the open position, the oscillating device of the .actuators Another feature of my invention is ployment-of loose pistons engaging opposite ends of the piston rods, which construction allows pressure to be applied in onedirection against the packing ofthe pistons and eliminates the drawing of air into the hydraulic system which frequently happens suction stroke.

My invention is illustrated inthe accompanying drawings, inwhichz Fig. 1 is a schematic view of one type of a compressor and a similar type of actuator. In this case both have double ended pistons with a rack,

` the rack meshing with the pinions; This figure shows longitudinal. sections through the compressor vcylinder and the actuator cylinder and shows a sectionthrough the vlocking valve, the

relief-valve being in elevation.

Fig. 2 is a detailed section on the line 2-2 of Fig. 1 in the direction of the' arrows.'

Fig. 3 is a longitudinal section taken on the line 3-3 of Fig. 5, withthe piston pinshown in elevation, through another formv of compressor,

v this being a rotatable screw type.

where a piston is moved in a of Fig. 7 in the direction of the arrows :through a I screw operated actuator, the screw forming part of the double headed piston and having splines formed integral with the screw.

Fig. 7 isa transverse section on the line 'l-'I of Fig. 6, taken in the direction of the arrows.

Fig. 81s a longitudinal section through another form of actuator, this havinga double ended piston connected to a drag link of a steering mechanism, the connection being through a slot in the cylinder. A

Fig. 9 is a transverse section on the line 8-8 of Fig. 8 in the direction of the arrows, illustrating the manner of clamping the cylinder to a iixed structure.

Fig. 10 is a longitudinal section through the combination pressure relief valve and auxiliary supply reservoir and valve.

Fig. 11 is an assembly drawing showing the connections of the compressor Vof Figs. 3, 4' and 5 with the actuator. units of Figs. 6 and 7, such illustration being somewhat in diagramv to conform with Fig. 1.

Fig. 12 is an assembly drawing of a compressor with the actuatorunit of Figs. 8 and 9, this likewise being somewhat diagrammatic to conform 'to Fig. 1. Referring rst to the construction ofFlgs. 1 and 2. In this case the compressor assembly designated by the numeral Il employs a cylinder l2. Ihis is formed of two similar ends I3 connected to a hollow supporting structure l4,.the

formsa rack bar having rackteeth 22 thereon.

Loose piston heads 23 contact the end of the rod and secured to each head there is a. piston cup 24,.

this being attached tothe head by a dove-tailed connection, the coupling preferably formed of rubber or the like. The hollow structure I4 has an enlargement 25 von one side accommodating a large driven gear 26 keyed to a shaft 21. This gear .is operated by a driving gear 28 housed' in an enlargement 29 of the hollow structure I4 on the opposite side of the cylinder. The gear 28 is connected to the rotatable steering post-36 vactuated byothe steering wheel 3l. A pinion 32 is keyed to the shaft 2l and mesh'es with the rack 22, thus `the rotation of the steering wheel 3| rotates thev driving gear 28 which in turn causes a rotaton of the driven gear 26, the shaft. 21, the pinion 32,- and a reciprocating motion to the piston rod which also forms a connecting rack bar.

pressure pipe line 35, this'being illustrated as having nipples 36 with connectors 31, a T 38, a main pipe 39 and 39 connected to one end of the T by a coupling 40.' To the'other end of the; ce)

T there is connected a combination pressure relief valve and suppl-y reservoir designated by the assembly numeral 4l.

The main pressure pipes 38 and' 39' are connected -to a lockcii valve 45. --This has a housing 46 with two ductsl therethrough and a trans- .verse duct 48. The rotatable stem 43 of the valve has a transverse port 56, this stembeing actuated by a handle 5I. The pipes 33 are connected to one side of the housing and on the `opposite side there is' a continuation of the supply pipes designated 55. and Each of these is attached to a- T coupling unit 56 and 56', 's from which extend pressure pipes 51 and 51 the actuator.

The actuator asl illustrated in Figs. 1 and 2 is identified by the assembly numeral 60 and employs a cylinder 6| clamped to the structure 62 which is to be turned. 'I'his is illustrated as having a spindle or rod 63 which is tobe rotated through an arc. The 'cylinder has closed heads 64 with connections 65 and 65' to the pressure pipes 51 and 51', respectively. Ingthe cylinder there is the double ended piston designated by the assembly numeral 10, this having a piston rod 1| with rack teeth 12 thereon. Loose heads 13 engage the end of the piston rod: These heads support the piston cups 14, the cups being secured to the heads by dovetailing or invany suitable manner.

A xed supporting structure 80 is shown as having va yoke-shaped bearing block 8|. This may be connected, for instance, to a fixed axle 82, or other similar structure, and forms a journal for the turning structure 62, this being illustrated as having a hub 83 (note Fig. 2) with a b ushing `84. An anti-thrust bearing 85 is used between the hub as and the upper end as of the yoke sl where the device is used, for instance, for a steering wheel of a vehicle.

A segmentalpinion 90 has pinion teeth 9| on its upper end. This pinion has a rod or shaft 92 extending through openings 93 in the ends of the yoke 8| and is secured from rotation by l a key or pin 94. Thus, the pinion is held stationary as regards the fixed structure 80. The

`cylinder 5| has an opening 95 in one .side with a hollow housing 96 connected thereto, this being provided with a cover cap 91. The housinghas a base 98 which may have a rotational bearing on the outer end of the upper yoke 86. This housing -accommodates the segmental pinion 90 having the pinion teeth 9|.

The manner of operating the assembly of Figs. 1 and 2 is substantially as follows:

When the stes-ring wheel is rotated in onedirection or the other a movement is given to the double en ded piston toward one end of the cylinder I3, thus exerting a pressure on the fluid at one end. This travels through the pipes 39 or 39 and when the valve 45 is in the closed position illustrated fluid is carried through the pipes 51 ,and 51' to opposite ends of the cylinder in the actuator and causes a movement of the doubled ended piston relative to the cylinder.

Then, on account of the segmental pinion 90 being held stationary and there being a relative movement between the rack and the pinion. the cylinder is caused to rotate a partial turn around the axis of a pinion as the center of rotation, thus moving the spindle orvrod 63. lThe valve .45 may be vopened by aligning the port 50 with the transverse ducts 4B, in which case when the compressor is operated the fluid has a free ow through the pipes 39, the ducts 41, 48, the port 50 on the plug 49 between the ends of the cylinder. There is also a free passage for the uid -at opposite ends of the actuator by means -of the pipes 51, 51', 55 and 55', through the same ducts and ports of the valve 45, but on account of the low frictional resistance to the movement of the piston by turning the rod or spindle 83, such spindle is movablev from the position occupied when the valve is turned to its open position.

The lock out valve 45 is illustrated in'Fig. 1

` in the position designated as closed, that is, the l transverse port 50 in the rotatable steml 49 is out |06 and above' this there is a shoulder I0. ange III has a cylindrical inside surface ||2 10 and described above is as follows;

end of the compressor cylinder and one end, of the actuator cylinders. It also affords direct connection from the opposite end of' the composition afording a vthrough connection by the by-pass 48 and the port 50, there is a free communication between the opposite ends of all of the cylinders. f

The combined pressure relief valve and supply reservoir 4| is 'constructed as follows, having reference particularly to Fig. 10:

This employs a valve housing which has a base IOI with an opening |02 therethrough, a. threaded neck I03,to which may be connected the head |04 on the upper end of the T connection 38, this beingv clamped by a coupling nut |05. The base has a lower flat valve seat |06/ with a groove |01, there being a central recess |08. A cylindrical bore |09 of larger diameter than the recess extends upwardly fromthe seat The immediately above the shoulder ||0 and an internal screw thread I I3. vA ring I I4 has a cylindrical bore I| and` it is provided with a lower surface IIB seating on the shoulder I|0 and is per valve seat. A screen I2I rests on the upper end of the ring II4.

. An adjusting pressure cap |22 is threaded on the upper end of the. cylinder II1 and hasa seat for a compression spring |23 bearing on the disk pressor to the opposite ends of the actuator cylinders, however when the valve is in its open piston |24, this being .backed by a piston cup |25.

The slidable valve plug designated by the 'assembly numeral |30 has a cylindrical surface I3'I sliding inside of the bore I|5 of the ring ||4 and has a flange |32 and a lower surface. A compression spring |34 seats on the shoulder, |35

of the base I0| and normally holds the valve plug seated on the upper valve seat, that is, the upper surface of the flange |32 engages the seat on the rim |I9.

Main ports |36 lead upwardly through the valve plug from above the rim to the upper surface of the plug, thus communicating with the cylinder \port |43 at the top of the plug. The stem of the plug has a fine bore |44, the end of which l|45 leads to the conical seat |42. The stem has a head |46 for adjustment. A loose straining packing |41 is confined by the coupling nut |05 in the lower part of the base ,|0I.

The operation and functioning of this relief valve and supply reservoir shown in detail in Fig. In the normal operation of the device the needle valve is adjusted so that when the fluid in the com-- -pressor and actuator system expands from heat, the excess fluid may slowly pass through the small bore of the stem and the plug |30 and be admitted to the cylinder I I1, causing an upward movement of the pistons |24 and |25 compressing the spring |23. In this normal operation the valve plug is held seated by the spring |35. In addition the excess pressure developed by the operation of the compressor also forces the valve plug |30 upwardly by pressure on the lower face |33 and maintains this plug seated so that the iiuid under pressure of the compressor cannot pass through the ports |36. Should there be a deciency of uid in the system including the` ing an unseating of the valve plug |30 from its upper seat and forcing this downwardly on the lower seat |06. There may then be a downward iiow of supply liquid through theports |36 and the grooves |01 to the piping system connecting the compressors and the actuators. andv thus at all times maintaining these properly lled with hydraulic fluid. It will thus be seen that this valve assembly 4| takes care of the expansion of. the fluid in the system and also the supply from a reservoir to make up a deficiency of uid in the system. f

It is to be noted that the needle valve of Fig. designated by the assembly numeral |40 which is manually adjustable is always open and thus may always transmit fluid between the reservoir and theA compressor and thus into the pipe of the compressor and actuator. systems or vice versa. The ow of course is regulated to be only at a very slow ratesuch as.drop by drop and' thus the directionof ow is dependent on the diiferential pressures between the reservoir and the compressor and the piping connecting between the compressor and the reservoir assembly.

I use other types of compressors and actuators than those illustrated in connection withFigs. 1

z and 2. Another type of compressor is shown in y and has a closure plug |63 threaded therein. -The upper end of the shell is castellated as indicated at |64 by having notches cut therein and a nonrotatablevring A|65 has lateral projections |66 which t in the notches |64. This ring has downwardly projecting bosses |61 engaging recesses |68 in the plug |63. The opposite end ofthe shell has'a closure head 69 iitted in the end .of the shell and secured thereto by radial screws |10. The shell is provided with longitudinal internal wide grooves |1| fora purposehereinunder detailed. These splines preferably extend from the plug |63 to the closure head |69,

A combined nut and sleeve designated is slidablyv mounted in the shell and hasa nut end |16 with internal threads |11. A sleeve section |18 extends downwardly from thenut inside of the shell and has external wide splines |19 engaging and 'guided in the longitudinal wide grooves |1| in the inside of the shell. A piston pin` |80 is connected `diametrically across the sleeve portion |18, the ends of the pin being conned by the inside of the shell |6|.

V A fixed cylinder |85 has its lower end |86 secured to the head |69 of the shell by longitudinally extending' bolts |81,thus confining the cylin der stationary. Such cylinder has a closure head |88. at the opposite end. The cylinder has dirametrically opposite longitudinal slots |89 to accommodate the lengthwise travel of the piston pin 80, such pin being moved longitudinally by lthe combination nut and sleeve designated above plugs |9|, each adapted at its inner` end |92 to contact the piston. pin |80. The opposite ends bf each piston plug have resilient piston cups |03 secured in place by dove-tailing or the like.

The oil circulation is provided by pipes 200 and 20|, the pipe 200 being illustrated as connectedto a nipple 203 in the closure head |69 at the lower end of the sleeve. The upper head |88 of the cylinder has a. transverse bore 204 and a longitudinal port 205 leading to the head of the cylinder. The pipe 20| leads through a perforation 206 in the lower head |69 and fits in longitudinal grooves 20-1 on4 the inside of the i a bent end 209, the end portion 2|0 being threaded in the bore 204. -Thus there is a hydraulic fluid connection between .both ends of the cylin-f der and the double ended piston. T he rotatable screw 2| 5 having external threads 2|6 engaging the threads |16. 'Ihis has an anti-friction bearing connection 2|1 with the cylinder head |88. The lower end of the screw 2|5 is provided with an annular recess 2|8 in which ts the annular structure for reciprocating the nut and sleeve as-A sembly |15 is as follows, and includes a rotatable projection 2|9 on the head |88; the packing ring 220 being used to obtain a seal. The opposite end of the screw 2|5 has an anti-friction bearing A22| engaging the underside of thev closure plug |63,

tls being h eld from rotation in the sleeve by the An operating stem 222 extends washer |65. through the head |63 and has a steering wheel 223 or the like secured thereto by a key 224 or the like. .A nut 225 is threaded on the end of the stem and rmly holds the steering wheel in place. which wheel may have a ange 226 extending over the outside of the shell |6| at the top.

The manner of operation and 'functioning vof the compressor of Figs. 3, 4 and 5 so far described, is as follows:

0n account of the shell |6| being held in a stationary position, the hand steering wheel or operating wheel |23 may bev rotated, which in its turn rotates the screw 2 I5. This causes either an upward or a downward movement of the combined nut and sleeve |15, the nut |16 having a threaded connection with the screw. This gives either an up or down or reciprocating motion to the piston pin |80. The cylinder |85 as above described is held stationary,'therefore the movement of the pin |80 in eitherdirection forces one or other of the piston plugs |9| of the pist n assembly towards one of the cylinder heads, thusI compressing the fluidat one end of the cylinder which the iluid is under pressure and maintains the opposite piston plug |9| in contact with the piston pin 80. It will thus be seen that a. positive hydraulic pressure may be developed at either end of the cylinder |85. y 1

As it is convenient to have a horn operating switch in the steering column,this is mounted as follows, having reference to Fig. 3, the assembly being designated by the assembly numeral 230:

-This employs av tubular plug 23| which leads through the sleeve |6| through a slot 232 formed at the'- sleeve ,|18 and is threaded into the head |88 at the upper end ofthe cylinder |05, this head having a bore 233. A'n insulating bushing 234 is iitted in theplug 23| and has an electrical conducting rod 235 fitted therein connectingat the outside to a terminal 236 fromwhich there is an electric lead 231. The inner'end of this rod has a contact knob 238. A complementary contact plunger or rod 239 leads through a longitudinal bore 240 in the screw 2|5 and the stem 222, this having a pusher knob 24| above the steering wheel and normally heldin an elevated position by the compression spring 242 which bears on the nut 225 and on the underside of the knob. Therefore -When the knob 24| is pressed downwardly it 'forms a conducting contact between the lower end' of the stem or rod 239 and the contact end 238; thus forming a ground connection which may beincircuit with a horn or otherI signalling device.

The actuator of Figs. 6 and 7 is constructed as A compound cylinder designated by the assembly numeral 2.56 is fitted in the bore-of the fixedstructure 25|. yThis has a lower rotatable part 251 rotating in the bushing 254 and 255 and has a closure head 258 at its lower end. This cylinder is provided with an internally threadednut v259 formed integral therewith. .The upper end of the and is hence non-rotatable.

cylinder 260 has an enlargement 26| at its upper end secured by a key 262 to the upper hub 252 An internal enlargement 263 at the bottom engages the shoulder 264 on the movable partof the cylinderassembly 251- and has splines 265. A closure head 266 is threaded or otherwise attached to the upper sta--` 'part of the cylinder 251 and has longitudinal splines 213 on its -upper portion engaging the splines265 on the enlargement 263 of the fixed part 260'of the cylinder 256. Pistons 214 having the piston cups 215 are loosely fitted in their respectiveA portions of the cylinder and adapted to contact the end of the combination screw and spline piston or piston rod.-

A movable steering stem spindle or axle 280 has a hub structure 28| surroundinglthe rotatable portion 251 of the cylinder 2,56 and secured thereto by a key 282 or other suitable fastening. Preferably anti-friction bearings 283 are 'located between the upper end of the hub 28| and the-upper hub 252 of the fixed structure.

The manner of operation and functioning of the actuator of Figs. 6 and 7 is as follows: When hydraulic pressure is developed in either the upper or the lower end of the combination cylinder made up of the stationary movable part- 251 andathe stationary part-26 through the medium of hydraulic fluid flowing through either of the pipes 261 or 268, the pressure on the piston cups and pistonsforces the combination spline and threaded piston rod 210 either upwardly or downwardly. As this is held from rotation by means of the spline connection `at 263, the nut portion 259 of the rotatable part of the cylinder is given a rotation in either one direction or the other n This xed structure is illustrated as havthe axis ofthe piston rod and of the combination cylinder. This develops an angular movement of the spindle 280 which may be used for instance for steering the wheels of a vehicle, the rudder of a vessel or the elevator of an airplane, or two of them working in opposite directions may be used to operate the ailerons of an airplane. This type of actuator is used with the connecting closure and control valve 45 of Fig. 1 and the combina tion reservoir and relief valve 4| shown and described in connection with Fig. 1.

The type of actuatorshownin Figs. 8 and 9 and designated by the assembly numeral 290, employs a substantial cylinder 29| which may be secured by a clamp 292 to a fixed structure 293. This cylinder has closure heads 294 and 295 at lits opposite ends and connections 296 and 291 for the hydraulic pipesl from the compressor. The cylinder 29| has a longitudinal slot 298. A plug piston rod 299 is mounted to reciprocate in the cyl- .inder arid contacting the ends of thisrod there are pistons 300 having piston cups 30| attached lthereto.

A swivel connection designated by the numeral 302 employs a block 303 secured by screws 304 or the like to the piston rod 299. .This block extends through theslot 298 in the cylinder and has a slidable cover sleeve 305 connected thereto, which forms a cover for the slot 298 and slides length- 4wise on the outside of the cylinder 299.v ,Formed integral with the block 303 there is a stud306 having a ball 301 at the end. This ball is connected to a drag link 308. This drag link has a head 309 with a spherical bearing surface 3|0. A

sleeve 3| is securely attached to the head 309 and a plug 3 2 having a complementary swivel surface is threaded and attached at the outer end of the one side to allow assembly of the ball 301 in the v sleeve and to accommodate the stud 306.

rod and has a swivel connection, the drag linkl may be operated in the direction either parallel to the cylinder or at a relatively small angle thereto, or in fact the drag link 308 will be at substantially right angles to the cylinder 29|, in

which case the motion of the drag link would be mainly an angular motion. On account of the hydraulic uid being forced out of the cylinder at the end opposite the fluid having the positive pressure, the piston 300 at the opposite end from the pressure end is maintained in contact with the piston rod 299. Thus by the internalpressure at both ends of the cylinder, the pistons form a contactwith the piston rod 299 and thus eliminate a loose action of this form of actuator. It is to be understood that thistype of actuator may be operated by the compressor shown in Fig. 1 or that shown in Fig. 3, and the assembly includes the combination reservoir and relief valve 4| and the shutoff valve 45.

Mypresent invention may be considered an improvement and further development of my patent application Serial No; 672,539, for Hydraulic steering devices, filed May 24, 1933 which has become abandoned.

This sleeve has an opening 3|3 on g Variousl changes may be made inthe details of my invention without departing from the spirit v thereof as set forth inthe accompanying claims.

I claim: s 1

1. In a pulsator mechanism including a double ended compressor cylinder and one or more double ended motor cylinders, each havingr double ended pistons combined with a hydraulic connection between opposite ends of the compressor cylinder and opposite ends oi! each motor cyllnder, said hydraulic connection including a combination reservoirA and pressure relief valve provided with a movable plug, means to normally seat the plug `to restrict tlow from the reservoir to the compressor cylinder, means maintaining a pressure on iluid in the reservoir, said pressure vmeans being adapted to unseat 'the plug to replenish fluid to the compressor cylinder and excess pressure in the compressor cylinder developing an additional pressure on the plug to maintain said plug in the closed position, a manually adjustable control valve mounted in the plug and adapted to' permit a slow passage of fluid from the compressor to the Yreservoir to transfer uid on expansion in the compressor to the reservoir.

2. In a pulsator mechanism as claimed in claim l, the hydraulic connection between the compressor and the motor cylinders including 'a' control valve, said valve having a housing with a pair of ducts therethrough, connections from one adapted to register with the port of the valve, the

said stem being rotatable to disalign the port o f the valvel and the said transverse duct on to align therewith,the said port when aligned with the transverse ducts giving a communication bef transverse duct directing the'hydraulic iiuid be tween the ends of thecompressor cylinder and the ends of the motor cylinder.v v

3. In a device' as described, a compressor having a double-ended cylinder, a piston rod and pistons therein, means to reciprocate the pistonrod and hence the pistons, an actuator having a double-ended cylinder, a piston rod with pistons therein, a hydraulic connection between the ends of the compressor and actuator cylinders, said connection having a combination'reservoir and:

. valve to always permit slow passage of lduid to and from the reservoir in accordance wtihdifferential pressures between the reservoir and compressor, the reservoir having means to exert a pressure on the fluid therein Y to unseat th plug and supply a deciency of fluid to the compressor, the actuator having means operative on a reciprocating motion of its piston rod to depiston rod ofthe actuator.

4. In a pulsator mechanism including a doublel'ended compressor cylinder and a double-ended motor `cylinder each having double-endedl pistons combined with-a hydraulic connection between opposite ends of the compressor and motor-cyl- Vinders including a combination reservoirandv velop a rotational l'movement between at least yj part of the cylinder, and a structure engaging the pressure relief valve provided with a movable plug adapted to seat on excess pressure from the com'- pressor and prevent entrance of iluid into the reservoir, means constantly developing a pressure on the fluid of the reservoir to replenish a deficiency in the compressor and a manually ad'- justable control valve to always permit a slow passage of fluid in either direction between the compressor and the reservoir dependent on the diierential pressures in the reservoir and compressor to transfer uid on Vexpansion in the compressor to the reservoir.

f CllARlLES U. BALLARD. 

